Variable MR imaging appearances of focal nodular hyperplasia in pediatric cancer patients

Focal nodular hyperplasia (FNH) is rare in the general pediatric population but is increasingly found in treated pediatric cancer patients. FNH can be incidentally found on CT and MRI and can be misdiagnosed as liver metastasis in patients with an oncological history. To describe the MR imaging findings of FNH in pediatric cancer patients. Ten children who had been treated for a primary malignancy and who were diagnosed with FNH from 2003 to 2010 were identified from a search for FNH in our pathology and radiology databases. Patients were included if they were treated for a primary malignancy and had undergone MR imaging of the liver including T1-weighted, T2-weighted and dynamic contrast-enhanced T1-weighted sequences. FNH from all patients (n = 10) demonstrated typical homogeneous arterial enhancement on MRI. The FNH was often multiple and small (7/10 patients), lacking a central scar, with variable imaging characteristics including signal hyperintensity on both T1- and T2-weighted images (4/10 patients), especially in the setting of hepatic hemosiderosis. FNH has a variable MR appearance in pediatric cancer patients and should be considered in the differential diagnosis of hypervascular liver lesions. (orig.)